Portion of floor cleaning machine



FIG. 1 is a perspective view of a portion of floor cleaning machine which embodies our design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof,

FIG. 5 is a right side view thereof; and,

FIG. 6 is a top view.

The details shown in broken lines form no part of the claimed design. 

The ornamental design for a portion of floor cleaning machine, as shown and described. 